Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing geologic formation. In subsea applications, structural casing may combine a low-pressure housing with a casing which is deployed into the seabed and set at a planned height above the mud line. Additionally, inclination of the structural casing is maintained within a maximum offset angle of, for example, 1.25° from vertical to facilitate interfacing with other subsea systems, e.g. blowout preventer, subsea tree, or tieback connector.
The structural casing may be jetted into position or set into a pre-drilled hole so the low pressure housing is close to the mud line but high enough above the mud line to allow remotely operated vehicle (ROV) intervention with respect to, for example, annulus valves. Generally, the height above the mud line is established via mud mats, mud sticks, and use of ROVs operated to assist in setting the elevation. The offset angle of the structural casing is monitored by a camera on the ROV looking at bull's eye targets. However, mud mats and mud sticks are substantial capital investments that are not recovered. Additionally, use of the ROV(s) tends to be relatively expensive and the cameras can be unusable for substantial time periods with respect to reading targets following a jetting operation to install the structural casing.